Photonic Imaging Array

• US 20180120085A1
• Filed: 11/03/2017
• Published: 05/03/2018
• Est. Priority Date: 11/03/2016
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Lane, Benjamin F., Spector, Steven J., Zhou, Alan X., Brown, Julian A., Moebius, Michael G.
• Granted Patent: US 10,731,964 B2
• Time in Patent Office: Days
• CPC Class Codes: G01B 9/02027 Two or more interferometric channels or interferometers
• CPC Class Codes: G01S 3/7867 Star trackers navigation using star trackers G01C21/025
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02B 6/12011 characterised by the arrayed waveguides, e.g. comprising a filled groove in the array section
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections
• CPC Class Codes: G02B 6/2813 based on multimode interference effect, i.e. self-imaging
• CPC Class Codes: G02B 6/2861 using fibre optic delay lines and optical elements associated with them, e.g. for use in signal processing, e.g. filtering delay lines in general H03H, H01P9/00; optical computing devices G06E
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262

Abstract

A multi-beam optical phased array on a single planar waveguide layer or a small number of planar waveguide layers enables building an optical sensor that performs much like a significantly larger telescope. Imaging systems use planar waveguides created using micro-lithographic techniques. These imagers are variants of “phased arrays,” common and familiar from microwave radar applications. However, there are significant differences when these same concepts are applied to visible and infrared light.

Claims

1. An imaging system having a design wavelength between about 100 nm and about 1 mm and a design bandwidth, the imaging system comprising:

a wafer;

a plurality of optical couplers disposed in a predefined planar array on a first layer of the wafer;

a plurality of optical detectors disposed in a predefined planar array on a second layer, different from the first layer, of the wafer;

a first optical phasing network having inputs and outputs, the inputs of the first optical phasing network being optically coupled to the plurality of optical couplers; and

a second optical phasing network having inputs and outputs, the inputs of the second optical phasing network being optically coupled to the outputs of the first optical phasing network and the outputs of the second optical phasing network being optically coupled to the plurality of optical detectors;

wherein;

the first and second optical phasing networks cooperate to form an analog 2-dimensional optical Fourier transformer.

2. An imaging system according to claim 1, wherein:

the plurality of optical couplers is organized as a plurality of rows of optical couplers and a plurality of columns of optical couplers;

the first optical phasing network comprises a first plurality of optical phasing networks, each optical phasing network of the first plurality of optical phasing networks having a respective plurality of inputs and a respective plurality of outputs;

each row of optical couplers is optically coupled to the plurality of inputs of a distinct optical phasing network of the first plurality of optical phasing networks;

the second optical phasing network comprises a second plurality of optical phasing networks, each optical phasing network of the second plurality of optical phasing networks having a respective plurality of inputs and a respective plurality of outputs;

for each optical phasing network of the first plurality of optical phasing networks;

each output of the optical phasing network is optically coupled to an input of a distinct optical phasing network of the second plurality of optical phasing networks.

3. An imaging system according to claim 2, wherein:

each optical phasing network of the first plurality of optical phasing networks comprises a respective Butler matrix; and

each optical phasing network of the second plurality of optical phasing networks comprises a respective Butler matrix.

4. An imaging system according to claim 2, wherein:

the first optical phasing network is disposed on a third layer of the wafer, different from the first layer of the wafer and different from the second layer of the wafer; and

the second optical phasing network is disposed on a fourth layer, different from the third layer, of the wafer.

5. An imaging system according to claim 2, wherein:

the first optical phasing network comprises a first plurality of stages of optical combination;

the first optical phasing network is distributed across a first plurality of layers of the wafer, one stage of the first plurality of stages of optical combination per layer of the first plurality of layers;

the second optical phasing network comprises a second plurality of stages of optical combination;

the second optical phasing network is distributed across a second plurality of layers, different from the first plurality of layers, of the wafer, one stage of the second plurality of stages of optical combination per layer of the second plurality of layers.

6. An imaging system having a design wavelength between about 100 nm and about 1 mm and a design bandwidth, the imaging system comprising:

a wafer;

a plurality of optical couplers disposed in a predefined planar array on the wafer, each optical coupler having an output and configured to couple an optical signal from free space to the output;

a plurality of optical combiners disposed in a first plane on the wafer, the first plane being parallel to the planar array of the plurality of optical couplers, each optical combiner having a plurality of inputs and a plurality of outputs;

a plurality of optical detectors disposed in a second plane on the wafer, the second plane being parallel to the planar array of the plurality of optical couplers, each optical detector having an input; and

a plurality of optical waveguides disposed in a third plane on the wafer, the third plane being parallel to the planar array of the plurality of optical couplers;

wherein;

the outputs of the plurality of optical couplers are coupled, in a hierarchical arrangement by the plurality of optical combiners and groups of the plurality of optical waveguides, to the inputs of the plurality of optical detectors, such that optical lengths of the optical waveguides in each group of optical waveguides are equal, within one coherence length at a bandwidth greater than about 0.1% plus a spacing between two maximally spaced-apart optical couplers of the plurality of optical couplers.

7. An imaging system according to claim 6, wherein each optical combiner of the plurality of optical combiners comprises a multi-modal interferometer (MMI).

8. An imaging system according to claim 6, wherein the hierarchical arrangement comprises an H-tree.